ISG15 and systemic lupus erythematosus: We found that the mRNA levels of OASL (median: 243.95, IQR 127.07–375.87 vs. 112.90, IQR 49.30–219.45, p = 0.002), MX1 (median: 859.20, IQR 369.92–1844.50 vs. 367.50, IQR 163.75–1172.00, p = 0.004), ISG15 (median: 0.31, IQR 0.13–0.59 vs. 0.13, IQR 0.06–0.32, p = 0.001) and LY6E (median: 258.30, IQR 164.77– 398.92 vs. 156.80, IQR 67.80–452.70, p = 0.05) in SLE with low C3 levels were significantly higher than those in patients with normal levels of C3 (Supplementary Table 3).